Telephone system



July 7, 1925.

' E. E; CLEMENT Tannrnous sxsrsu Filed June 5, 1905 2 Sheets-Sheet 1July 7, 1925.

E. E. CLEMENT TELEPHONE SYSTEM 2 Sheets-Sheet 2 wuuma Patented July 7,1925.

UNITED STATES PATENT OFFICE.

EDWARD E. CLEMENT, OF WAfiHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR, BYMESNE ASSIGNMENTS, TO THE NORTH ELECTRIC MANUFACTURING COMPANY, A

CORPORATION OF OHIO.

TELEPHONE SYSTEMI.

Application filed June 5, 1905. Serial No. 268,784.

To all whom it may concern:

Be it known that I, EDWARD E. CLEMENT, a citizen of the United States,residing at lVashingto-n, in the District of Columbia, have invented acertain new and useful Improveinent in Telephone Systems, of which thefollowing is a specification, reference being had therein to theaccompanying drawing.

My invention relates to telephone exchange systems, and constitutes animprovement in that type of systems which I have denominatedsemi-automatic, wherein a connection is initiated by an operator,manually, and is completed through the medium of mechanism controlledfrom the subscribers station. The object of the invention is to producea circuit of the two-wire type, which will enable existing installationsequipped with manual apparatus to be remodeled and their capacityincreased by the addition of automatic apparatus without substantialchange in the manual portions, or in the circuits.

While, as I have stated, the invention has to do particularly withsemi-automatic systems, I contemplate applying the principles involvedto full automatic installations, in a manner which will be pointed outin the detailed description and statement of oper ation.

Briefly stated. the present scheme involves the use of a plain metalliccircuit throughout, all operations of talking, and signalling beingconducted over or controlled through this circuit. All working impulsesfor signalling and switching are sent over one side of the circuit only,the working magnets being sensitive or quickly responsive, and a controlmagnet of sluggish nature responding to long makes or long breaks tobring the various pieces of apparatus into circuit in required sequence.This control magnet, actuating a suitable switching device, takes theplace of the usual so-called side switch in automatic systems.

My invention is illustrated in the accompanying drawings, wherein Figure1 is a diagram showing a subscribers line and an operators connectivecircuit. Figure 2 is a diagram constituting a continuation of Figure 1,showing a switch trunk and another subscribers line.

Fiiure 3 is a plan View of the pilot switc Figure 4 is a side view ofthe magnet and ratchet.

Referring to Figure 1, A is a subscrihers station equipped with theusual transmitter T, receiver R, switch-hook H, condenser C and ringerQ. This station is connected to the central oflice by line-wires 12',terminating in relay contacts m, m of the cutoff relay N. These contactsare normally in engagement with other contacts n, a, the first connectedby wire 5 through relay M to the main battery B, and the second toground. The contacts n, n are taken away from their normal restingcontacts where the relay N is excited, and brought into engagement withother contacts n n, connected to the line jack J, in the spring andsleeve sides of the same, through the wires 3-4, and also through wires7-8 to the multiple contacts J which are disposed in automatic switches.

The cord-circuit shown terminates in an answering-plug P and acalling-plug P, each with tip and sleeve contacts p, 1), connectedthrough cord conductors 911, 10-12, broken by condensers C, C. The mainbattery B is bridged across each end of the cord through a pair ofrelays. On the answering end the controlled relay S is between thebattery and the sleeve side, and

the supervisory relay S between the battery and the tip side, the formerbeing a front contact relay and the latter a back contact relay. Thesetwo relays jointly control the local circuit of the superviwry lamp 8.On the calling end of the cord the arrangement is the same, thecontrolled relay S and the supervisory relay S jointly governing thecircuit of the supervisory lamp 3 In the callingend of the cord is alsoincluded the ringing key K, which may be provided with listeningcontacts, if desired, but in the present system is not so shown.

So far, the circuits and apparatus are all of a well-known type, and asI describe my additions thereto it will appear that this much, which isthe essential and distinguishing part of the manual system, remainsunchanged. I add to but do not alter the cord or line-circuit. In amultiple-switchboard the wires 3-4 are connected to the minitiple-jacksthrough the branches 7.-8; and here the first difl'erence occurs, for Idiscard the multiple jacks, and substitute the terminals J in the banksof the switches.

At the subscribers station it is necessary to provide some means forsending impulses in predetermined order. These all go over the No. 1side of line, hence it is possible to make and break the circuitmanually, or to use an automatic sender such as the regular standardautomatic electric sender in common use with the so-called Strowgersystems. In fact it is entirely possible to use the ordinary switch-hookwithout any change whatever. This is manipulated to send successiveshort breaks in groups, leaving the line closed for an appreciable timebetween the groups, the number of breaks in each group corresponding toa digit of the number wanted. Thus in sending the number 4436, thesubscriber would remove his receiver from the hook, and listen. InFigure 1 I have shown the special variable tone generator G connectedthrough a condenser C to the wire 5, so that as long as the line isconnected to the line-relay M a characteristic sound will be produced inthe subscribers receiver. Even without this, however, the subscriber cantell when the plug is inserted, because it the circuits are traced itwill be found the battery is reversely connected to line when the plug Pis inserted. Having waited until he hears the plug inserted, knowingthis either by the cessation of sound from generator G or by hearing theloud click due to the bat tery reversal, the subscriber taps his hooksharply and rapidly four times, then after a short interval during whichit remains up he taps it four times more. As soon as he has done this hewill hear the battery cut off by the opening of contacts 2 2 in the sideswitch, and he will then wait until battery comes on again, in themeantime if the generator G is employed the tone signal becomingaudible, inasmuch as the cut-off relay N has lost its current. IVhen theplug P is inserted in the trunk jack J the relay S pulls up, the sideswitch Z moves forward a step, and the contacts 2' .2 are again closed,whereby magnet N again takes current, relay M and generator G orreversed battery B are cut ofi', and the subscriber knows he can goahead. He then taps the hook three times, and after an interval sixtimes. The description of this operation sounds somewhat involved, butreally it is simple in the extreme. The subscriber has only to rememberthat when he hears the musical note of generator G he must wait until itceases before he can signal. It almost goes without saying that aphonograph might be substituted for generator G giving oralinstructions.

I believe I am the first to produce a metallic circuit automatic systemwherein only the standard subscribers instrument, line circuit, andswitchboard apparatus are employed; I am also the first in any kind of asystem, so I believe, to use an ordinary telephone set without anautomatic sender, by manipulating the hookswitch.

In Figure 1 I and W are two sending wheels, or two pairs of sendingwheels, the one, VV', adapted to be set by the subscriber independentlyto the desired thousands and hundreds digits; the other W adapted to besimilarly set to the desired tens and units digits. These two pairs ofwheels, as well as the cams, 10 and w and the detent wheel, 00, with itsmagnet, IV, are housed in a casing adapted to be clamped or other wisesecured to any common battery telephone. The wheels named are preferablyall on the same shaft, or on separate shafts geared together, and allthe parts are shown in the figure in their normal or idle position. Whenthe wheels have been set a handle is turned whereby the spring of aclockwork train is wound, and the detent on the armature, a, of themagnet, W, then retains the signal. The cam, 10 turns with the wheels.W, coming into the position shown, with the spring, 10 resting in itsnotch, when the thousands and hundreds wheels have run down. The cam,1.0 on the other hand, runs with the wheels, W and comes to zero withthem, after the units and tens have been sent.

The magnet, W, releases the train when it is energized, and opens thesignalling circuit to line through the branch 58.

Associated with the cord-circuit is an indicator shown as comprising twostep-by-step discs, each adapted to be set around by a magnet I or I, aretaining pawl being provided for each disc, and a restoring device, IThe indicator magnets, I, I are each grounded on one side, and areconnected back through wires 22 and 220 to the contacts 2 and .2 of thecontrol or pilot switch, Z.

The shitting or pilot switch Z consists of a spindle with a ratchetwheel and a magnet to turn the same, the latter being shown at Z, andthe movement substantially the same in kind as in the indicator. Thisratchet wheel is held at each step by a detent pawl. which mayconveniently be released at the end of a conversation either by thesamemanually operated button, I which releases the indicators. or by anelectro-magnet. The operation of this switch is shown in Figures 3 and4. On the spindle of this switch are mounted arms or a cam drum.sweeping over contacts step-by-step as the ratchet wheel is turned.These contacts are shown in Figure 1 in pairs, supposed to be opened andclosed successively as the cam drum is turned. At the first step thepair 2 2 is closed. to cut in the thousands indicator magnet. I; at thenext step this pair is opened and the next pair, 2 z" is closed to cutin the hundreds indicator magnet, I; at the next step this pair isbroken, and the next pair, 2 2* is closed to connect the battery wire240 by way of wires 17 and 21 to the conductor 11 and so through the tipof the plug to the tip side of the switch trunk, so as to repeat thefollowing impulses around the condenser, G, into the trunk circuit; thissame step opens the battery circuit through wire 14 by opening thecontact pair, 2 2 which is normally closed. There is then one more stepto this switch, by which the pair 2 z are again closed and the pair 2 2left closed. The final step or restoration then preferably cuts off thewire 21, although this is not absolutely essential, as during conversation the magnet, S would form a shunt for the other groundedconnections. It is better, however, to give the side switch the finalstep, leaving the pair, .2 2 closed and all the other pairs open, so asto have a clean cord-circuit.

Referring now to Figure 2, J is one of a group of trunk jacks located infront of each 0 rator, each trunk line, 31 and 32, prefera 1y appearingon a jack J in multiple at every section of the switch-board. The trunkcomprises two wires 31 and 32, the former normally open everywhere, thelatter connected only through the relay S to ground. When a plug isinserted in a trunk jack the magnet S gets current through the sleeveside of cord and magnet S and pulling up closes the ti side 31 of thetrunk to relay S and grou'n Impulses coming over the tip side thereafteraffect this relay,

which corresponds to the supervisory relay S of the cord-circuit. Eachtrunk is provided with a side or pilot switch by manipulation of whichthe different pieces of apparatus are succesively brought into properrelation with the relay S and other parts of the circuits and apparatus,as will be fully explained in a moment. This switch is designated forconvenience Z", and is in every respect similar to the switch Z in thecord circuit. Each of these switches has an operating magnet forstepping its arm around a step at a time, this marked Z in the cordcircuit, Figure 1, and Z in the trunk circuit, Figure 2. Each switch iscontrolled by a solenoid or other slow relay S which is quick to beenergized and pull up its arma ture or core, but very slow to fall backand close the circuit of the stepping magnet. This sluggish action isaccomplished by means of a noninductive shunt circuit (66 in Figure 1,99 in Figure 2), around the relay Z and S", respectively. This solenoidor slow magnet is marked Z in Figure 1. and S in Figure 2. Each switchhas a spindle and an arm or arms and contacts, as already set forth.

The trunk line til-+32 (Figure 2) has for its terminal a Selectiveswitch P through which the connection initiated by the operator withplugs P and P, may be completed. This switch may be of any well known orusual ty e in which two motions or two selective di erentiating acts areemployed. Such a switch is shown in Letters Patent 815,176, granted toKeith and Erick son, March 13, 1906.

l have shown the terminal contacts of the switch at 29 p and haveindi-cateo the spindle at s". The multiple line-contacts are shown at JThe trunk wires 31 and pass to contacts 3 and 7 being also connected tocontarts 2 and These contacts are normally open, the former pair beingcontrolled by the test relay Y and the latter by the pilot switch Z".The wipers 39 p are connected back by wires and 34 to the con tacts 3 3of the test relay. normally touching the generator contacts 2 3 andwires 33 and are also connected to the contacts and 2 of the pilotswitch. At a point between the generator G and the sleeve-side wiper 39the wire 45 is connected to a choke coil to the main battery B, thisbeing for the purpose of holding up the cut-off relay N while ringing. Abusy-back generator G, preferably working through a condenser isconnected across the contacts y, y of the test relay, these contactsbeing crossed together with the contacts 1 and y when the relay Y isenergized, but insulated from the contacts 3 and y.

X is the release magnet. for the switch, and is connected from ground bywire 42 to the Contact 2" of the pilot switch. The generator circuit45-46 also passes through a pair of contacts 2 2, and the test relaycircuit 43-44 passes through a similar pair 2 2 of the pilot switch.

At the righthand end of Figure 2 is shown a subscrihers line-circuit andits con nccted apparatus, for a sub-station A, similar to that of A.

The operat on of my system will now be stated.

ssume that subscriber A desires to be connected to subscril' er .g. Hefirst sets his sender l to the desired number. which we will assmne tobe 3364. He then removes the receiver from the switch-hook. and we findthe following circuit conditions: the talking circuit 50, 52, 53, brokenat w by cam m circuit for line-relay M completed as follows: B, M, 5, n.n, 1, 55, 20 0 w. 10 56, 57, W W731. 5 3. 2 n". 77 ground and back tobattery. It will be underst od that while l have shown the wheels W, asseparate. each with its own pair of contact pens in series. both beingclosed when the wheels are set. this is for purposes of illustrationonly. For a number of four digits there should be four wheels, but thereneed be only one pair of pens. The four wheels can be set separatellf)Tel

ly, the teeth on each following the teeth on its next neighbor, and whenrunning down they can and preferably will turn as one.

The current through the circuit traced lights the line-lamp m, byenergizing the relay M. The operator, perceiving the signal, inserts theplug P, thereby putting battery on the sleeve side of line by thefollowing path: B, 24, S, 14, 2 .2 p, 7", 4 (then through cutofi' relayN to ground and also), to 2, 10 w", 54, IV and ground. The cut-off relayhaving pulled up takes off the relay M and wire 5, as Well as the groundfrom contact a, and puts linewires 1 and 2 through 3 and 4 to the jackJ. Current through magnet IV causes it to pull up its armatures w, oneof which releases the wheel on and starts the wheels to, while the otherpermits the terminal spring of wire 58 to bridge across the wire 53. Thetrain W runs down, sending the first number in a series of short breaksover the circuit B, 24, S, 14, 2 2 p, j, 4, n n 2, 53, 58, 57, 56, w, w,to, w, 55, 1, n, M, 3, p, 13, S and ground, whereby the relay S iscaused to vibrate its armature, opening and closing a circuit which maybe traced as follows: B, 24, s s, 240, s. 8 17, .2 2*, I, ground back tobattery. Each short break puts battery onto this circuit, that is eachshort break in the line-circuit producing a corresponding make in thelocal circuit just traced, and causes the magnet Ito advance itsindicator one step. The number of impulses in the first set determinesthe number to which the first indicator is stepped around.

At the same time that magnet I gets its first pulsation of current, therelay Z which is connected in parallel therewith through the wire 17also takes current, and instantly pulls up its armature, which is madevery sluggish in returning, so that on the succession of short breaks inthe local circuit due to the short makes in the line, the armature willnot fall back far enough to close the circuit of magnet Z. At the end ofthe first set of impulses, however, the first wheel V at the subscribersstation produces a long make (or if the subscriber is manipulating theswitchhook he lets it stay up for a moment). The effect of this is tocause relay S to hold up its armature and thereby cut off current fromthe relay Z long enough to permit the armature of the latter to fall allthe way back and close the circuit 18 of the magnet Z as follows: B, 24,s s 19, 18, Z, ground. Magnet Z then pulls up and steps the side switcharound, opening the springs .2 a and closing the pair 2, .2. The firstbreak in the line of the second set, as the subscribers wheel Wcontinues to run, produces a corresponding make in the circuit of magnetI, and of relay Z the second indicator disc thus being started and thecircuit 18 being again broken. \Vhen this second set of breaks has beencompleted, a long make in the line again holds up the armature s andlets the armature of Z close the circuit 18 and step around the sideswitch, opening the contacts a, 2 and a The indicator magnets I, I arethus cut off entirely and the battery supply through the wire 14 is alsocut off from line-wire 2 and the cut-01f relay N, the latter perinitingits armature to fall back, and the magnet W losing current andpermitting its armatures to fall back to open the circuit 53, 58. Theline-lamp m may now glow, and if the subscriber is using his switch-hookfor a sender he will hear the tone of generator G and the operator,perceiving the number which has been set up on the indicator by themagnets I, I, takes up the plug I and inserts it in the trunk jack J ofa group bearing that number. There may be anywhere from 2 to 15trunkjacks in a group, depending upon the percentage of lines which willbe in use at once. In order to determine which of these are idle theoperator may test them in the ordinary way, hence my reference tolistening contacts in the key K. The test circuit is simple. It will beobserved that the sleeve side of the trunk, 32, is normally to ground,but when a plug is inserted in any one of the trunk jacks the potentialof the sleeve side is raised by the connection of the battery throughthe sleeve side of the cord.

As soon as the plug P is in the trunk jack the following circuit isestablished: B (in the cord), 24, S 16, 12, p. j, 32, 41, .2 2 35, P Sand ground. The two relays l S thereupon pull up. The former closes thefollowing circuit: B, 24, s", a 20, 19, 18, Z, ground. Magnet Zthereupon steps the cord side switch around one more step, closes thecontacts 2 z, and also closes the contacts a and .2 The former closureputs battery back on the sleeve side of subscribers line, 2, againenergizes magnet W, and lets the second pair of wheels W start. If thesubscriber is manipulating his switch-hook he hears the generator G gooff and the battery B come on. The relay S on the other hand, pulls upits two armatures, and closes the following two circuits: From battery B(in Figure 2), wire 40, s, s", 8 and if the relay S be deenergized, tos", magnet Z to ground; also from wire 31, 36, s 8 37, .2 2 39, S, andground. Now, since the wire 21 in Fig. 1 has connected the point 8 t0the tip conductor 11 of the cord, it is obvious that the breaks comingin over line 1 and causing the armature s of relay S to fall back, willproduce a corresponding series of current pulsations over the followingpath: B (in Fig. 1), 24, s s, 240, 8, s 17, a", a 21, 11. At the pointof connection with wire 11 the current divides, a portion going by eachof the following paths: first, wire 15, relay S and wire to ground andback to battery; second, through conductor 11, to p, 7', 31, 36, s, 837, relay C and to ground; also 37, 2 2 39, and S to ground. None ofthese parallel paths will affect the others because they are directly tobattery without any intervening resistance, but care should be takenthat all the contacts and wire connections have a suflicient currentcarrying capacity to supply the three paths without burning out or undueheating.

Thus as the impulses come from the subscribers station due to the secondpair of wheels, they are repeated by the relay S around the condenser Ginto the tip side of the trunk. These impulses coming over the wire 31affect the magnet S, which is one of 'the two stepping magnets of theautomatic switch P .As .it takes the impulses the wipers p are moved,vertically or in a rotary direction according to the type of switch, thevertical movement coming first if a Strowger switch be employed, and ineither case the tens group of line-contacts J being selected in whichthe terminals of the wanted line are to be found. At the end of this setof impulses there comes a long make, as .before, whereupon the armature.9 remains back long enough to make contact with the point 8 and byenergizing the magnet Z to step the side switch Z around one step,thereby opening the springs 2 2 and closing 2, 2, thereby putting wire37 through wire 38 to the second magnet S of the switch P this being themagnet which in the Strowger switch moves the wipers around the row, toselect the unit contacts wanted.

When the side switch in the trunk worked the last time, the switch Z ofthe cord also moved a step; but no effect was produced thereby, thecontacts 2 2 being maintained closed during both steps. As the last orunits impulses now come in as breaks over the line, they are repeated asbefore over wire 31, to energize magnet S, as stated. At the end of aset of impulses the long make comes, armature s in the cord stays up,and the relays Z and S of the side switches of the cord and trunk, fallall the way back, and both side switches are advanced a step. The switchZ does not open the contacts a", 2 until the switch Z makes its step tocut on 2 2 and 2 2 The switch Z opens the contacts 2 .2, therebydisconnecting the magnets S and S and closes the springs 2 2 therebyconnecting the test relay Y to the wiper vp by the following path: Y,43, 2 2 44, 34. As this wipe-r rests on the sleeve contact of the wantedline, if the sleeveside of that line has its .potential raised becauseof another connection existing, the magnet Y will instantly take currentand will pull in its armatures thereby disconnecting the generatorcontacts 3 and 3 and bridging the busy-back G across the wires 31, 32through the insulated contacts g, 1 3 y". The calling subscriber thenhears the buzz of the busy-back, or if desired the voice of a phonographsaying Line is busy. The subscriber thereupon hangs up. A wire 47, itwill be noted, connects as a branch of the wire 42 to the front contact3/ of the relay Y. hen the relay Y pulls up therefore, it puts therelease magnet X on the Wire 32 through the contact 3 and the magnetimmediately takes current and pulls up. As 3 commonly used in automaticswitches this what is called a two-step release, that is the magnet whenit pulls up simply hooks its lever onto the release end of the detentpawls of the switch, and when it lets go the retractile spring of itsarmature is strong enough to pull off the pawls and so let the switchreturn to normal or inoperative position. Hence the switch remains setafter the subscriber hangs up. When he hangs up, however, the operatorperceives by the lighting of the supervisory lamp 8 that he has done so,and thereupon pulls the plug P out of the jack J. This cuts oil thecurrent supply from the magnets S and X, and as the latter then lets goits armature, the switch is forthwith released. By Winding the magnet Yhigh and making it of considerable impedance, the amount of currentabstracted from a busy circuit and the consequent annoyance to busysubscribers is no more than in any testing operation in systems now inuse.

If the line wanted is not busy, the magnet Y gets no current when theswitch wipers come to rest on the line terminals J, and the procedure issomewhat difi'e'rent. It should be stated here that after the last teethof the set for number transmitting on the subscribers wheels W there aretwo or more teeth which are always operative for the purpose of settingthe side switch Z". The side switch Z is unaffected after it makes thefinal movements stated, either because its arms have reached a stopwhich prevents further movement, or because the last steps go over tiedcontacts or solid contacts so as to maintain condi tions unchanged. Theside switch Z has 5 movements, however, and if we cause the insertion ofthe plug P to give the first movement and cut in the magnet S simply byputting battery on at J and through the closure at s -s putting batteryon Z before S is energized, which is the proper and economical course,still the subscriber only gives two long closures after that, by whichmeans we are brought to testing, but the wanted line must still berungand the circuit then put through. So

two more invariable breaks of short duration are provided just beforethe W wheels run down. If the line wanted is not busy, the next breakcomes in, in due course, and the side switch Z makes another step,closing the generator contacts 2 and 2 which may be on one side asshown, or double-pole if desired. This puts generator to the wantedline. After any desired and predetermined interval the last break comes,followed by the final make as the cam 'w closes the talking circuit505253, at the substation, and the switch Z makes its final step,opening the generator contacts, leaving the test contacts open, andtaking spring 2 off spring .2 and putting it on 2", thereby cutting offthe relay S and cutting on the release magnet X, which immediately pullsup and remains on the sleeve side of line during the conversation.Everything else is disconnected, however, including magnets S and S andwire 36. The same step of the side switch closes the contacts .2 z and zz whereby the trunk is prolonged to the Wipers, with the same cleartalking circuit as in a manual trunking system, and with nomore contactsthan any, but less than most, to talk through.

After the trunk is completed, the two supervisory relays S and S in thecord circuit are responsive to the two subscribers, as usual, and if thewanted subscriber does not answer within a reasonable time, the operatorcan ring him again by means of the key K, also as usual. This will notoccur except in a small percentage of cases, and in fact automaticrepeating of the ring can be arranged by merely giving the subscriberssender more ringing teeth and the switch Z" more steps or a set-back. Ifhe finally fails to answer, the operator will withdraw the plug P andinsert it in a busy back jack of usual pattern and connection, or canput the caller onto a manual or chiefs desk to be talked with andsoothed if necessary. The subscribers operator under no circumstancesattempts to talk, and in fact she cannot, having no equipment for thatpurpose, unless speed of service is to be sacrificed. She does not needto talk in the ordinary course of business, for if the steps inoperation are followed carefully it will be observed that she getssignals for all that are perfectly plain. The line lamp lights when theman calls, and may also light after the first two numbers have come in,denoting that attention is required to insert the plug P. Thesupervisory lamps flash as the signals go through, and respond to allthe movements of the subscribers afterward.

When the connection has been completed and the subscribers finishconversation, they hang up, and the supervisory lamps announce that theydesire disconnection. The operator then pulls the plugs and themechanism restores itself.

In case the calling subscriber desires a 're call he flashes his lamp,or if the wanted subscribers lamp continues to glow while the callingsupervisory remains dark it may denote the same thing, although it isditficult to distinguish this from the condition when the subscriber hasnot answered, and the operator then pulls the plug P, leaving the plug Pin the jack. The indicator II and the side switch Z being at the sametime restored to normal or Zero position, the operator pressing thebutton 1", the subscriber can get another number at once. He must set uphis sender, of course, or manipulate his hook as before.

In the manner of showing the circuits in Figure 2, it is to be observedthat the generator G and busy-back circuits are both tied onto one sideof the trunk during conversation. It will be understood, of course, thatdouble-pole cut-offs or switches are to be used throughout so theseconnections will not exist in practice, but are shown herein because ofa desire to simplify the drawing as much as possible. Such connectionswould make the lines noisy.

In case the sender VVW be omitted and the switchhook be used in lieuthereof, all the circuits and apparatus of the sender would beeliminated, leaving the circuit that of any common battery telephoneset, impulses going over the following path when sending: (see Figure1): B, 24, S, 14, .2 2 p, j, 4, n n 2, 53, 52 (sender being omitted andthe wires 58 and 52 tied together) T, R, H, 50, t, a, n 3, j, p, 13, S,and ground.

In practice the magnets Z and S may be solenoids or other sluggishmagnets which close their local circuits only on a long break in theenergizing circuits.

Having thus described my invention, what I claim and desire to secure byLetters Patent of the United States is:

1. In a telephone system, automatic switching apparatus, a controllingmagnet therefor, auxiliary circuit changing apparatus, a controllingmagnet therefor, a common control circuit, a connection from saidcircuit to the auxiliary magnet, and a connection also from said circuitthrough contacts in the auxiliary circuit changing apparatus to theswitching magnet, each of said magnets being adjusted for a timeconstant such that one magnet will not respond to changes which willaffect the other, substantially as described.

2. In a telephone exchange system, a two- Wire metallic line circuitwith common battery at central, a sender having means to make and breaka circuit, and an automatic switch having two-wire connections, connective circuits, and an auxiliary or sideswitch, said side switchcontrolling the sequence of operating steps of said automatic switch andthe connections of the operating parts of the connective circuits, andhaving a different time constant from the main switch, whereby thelatter may be operated without operating the former, substantially asdescribed.

3. In a telephone exchange system, a subscribers line terminating in ajack, an operators cord circuit terminating in plugs, a supervisorysignal magnet connected with the line through said cord circuit, and anautomatic switching apparatus operated by said supervisory magnet,substantially as described.

4. In a telephone exchange system, a subscribers line and substation,with means to make and break the line circuit controlled by thesubscriber, a common battery for a plurality of lines at. the centraloffice, connective circuits initially controlled by an ii operator, asupervisory signal magnet connected with the battery to the subscribersline through the initially established connective circuit, and anautomatic switch responsive to makes and breaks as to its operatingparts, in a circuit controlled by the supervisory magnet, substantiallyas described.

The telephone system comprising a common battery two-wire manual circuitwith connecting cord having associated supervisory relays and lamps,control relays for the battery supply for said lamps, a two wireautomatic trunk having a switch with controlling magnets adapted to besuccessively cut in for stepping to a desired line terminals, anauxiliary or side-switch tor the main switch having magnets withdifferent time constants from those of the main switch and controlledthrough the same or associated circuits, and means at the subscribersstations to produce changes oi? different durations to control therespective switches, substantially as described.

(5. A telephone exchange system comprising line circuits, connectiveapparatus therefor arranged in successive links, one of said linkscomprising automatic connective means controlled by a callingsubscriber, an operators signal receiving position and supervisorysignals at said position adapted to indicate the progress and conditionof a connection.

7. A telephone exchange system having combined manual and automaticconnective apparatus at the central office, sending ap-' paratus at thesubscribers stations, and means at the central office becoming effectivewhen the manual apparatus has been actuated and the connection isinitiated,

to inform the subscriber of the condition of the circuits.

8. In a telephone exchange system, subscribers lines, manual means forinitiating connections therebetween, automatic apparatus therebyrendered available and placed under control of a calling subscriber, andsignalling means simultaneously informing the subscriber of thecondition of the circuits.

9. In a telephone exchange system, a plur'ality of line circuits to beinterconnected, manually operated means for answering calls andinitiating connections, automatic switches thereby brought under controlof the calling subscribers, automatic signalling means to apprise acalling subscriber of the condition of the circuits, and supervisorysignals associated with the manual connective means also under controlof the calling subscriber.

10. In a telephone exchange system, subscribers line circuits, a centralstation, apparatus at said, station comprising both manually operatedand automatic connective links, means for bring said automaticconnective links under the control of the calling subscriber, and meansfor automatically apprising the subscriber of the condition of thecircuits.

11. In a telephone exchange system, subscribers lines, a central stationprovided with apparatus comprising both manually operated and automaticconnective links, means associated with said manually operated links forautomatically indicating the group containing the desired automaticconnective link, and means for placing the automatic connective linkunder the control of the calling subscriber.

12. In a telephone exchange system, a subscribers line and sub-station,means controlled by the subscriber to make and break the line circuit, acentral station, automatic and manually operated connective linksthereat, mechanism associated with said manually operated links toindicate the group containing the desired automatic connective link,said mechanism being responsive to the makes and breaks of the callingsubscribers line circuit, and said automatic connective mechanismoperating to effect a talking connection and being also controlled bysubsequent makes and breaks in the subscribers line circuit.

13. In a telephone exchange system, a plurality of metallic linecircuits, a number of automatic switches less than the number of linesfor purposes of interconnection, auxiliary apparatus including means forsignaling wanted subscribers associated with each switch, local orbranch circuit connections for the auxiliary apparatus and for theswitch, electromagnets controlling the switch in its movements, and thelocal circuits and auxiliary apparatus, said magnets having differenttime constants, means to connect a calling line to an idle switch, andmeans associated with a line when calling to produce current changestherein of different durations and according to a predetermined code,whereby such changes in the metallic circuit, without the use ofgrounds, may effect and control the switch movements and operate theauxiliary apparatus associated therewith, in proper order and sequenceto select and call a wanted subscriber.

14. A telephone exchange system comprising a control circuit, associatedautomatic switch mechanismhaving waiting contacts divided into groupsand a co-operating moving contact, a primary magnet and associated meansfor stepping said moving contact to a desired group of waiting contacts,a secondary magnet and associated means for stepping said moving contactto a desired contact in that group, quick and sluggish relays forcontrolling said magnets, means for energizing and deenergizing saidrelays by closing and opening said control circuit to operate saidprimary and secondary magnets to bring about the desired movements ofsaid moving contact.

In testimony whereof I have afl'lxed my signature in presence of twowitnesses.

EDWVARD E. CLEMENT \Vitnesses:

JAMES H. MARK, E. EDMONSTON, Jr.

